Workpiece holding assembly

ABSTRACT

A workpiece holding assembly for a machine apparatus is provided having an adjustable rail clamp attached to a rail which is secured to a work table of the apparatus. The rail is provided with front and back side referencing surfaces and the rail clamp includes an inner channel having an inside wall which comprises a reference surface for engagement with either the front or back side surfaces of the rail. The rail clamp includes a rail fastener means which functions to create a downward and inward force component which securely draws the inside wall against the rail reference surfaces to ensure a solid rigid connection. The rail clamp further is provided with a leveler connector means providing a quick release with a leveler head. The leveler head is provided with a connector portion that forms a corresponding connection with the leveler connector means. The leveler connector means includes a manually operated lever that draws the leveler head and rail clamp together so that reference surfaces become rigidly engaged in a manner to orient the leveler head in a predetermined relationship relative to the rail. The leveler head includes a cant adjustment means comprising a pivot part and two jack screws oriented in a triangular pattern so that movement of either of the jack screws will tilt the leveler head in whatever angular disposition is desired. The leveler head further includes a horizontal adjustment means comprising a cam which operates against a corresponding opening in the top surface of a workpiece clamping means. Rotation of the cam slides the leveler head horizontally relative to the workpiece clamping means. The leveler head also includes a vertical adjustment screw which moves the leveler head vertically relative to the rail clamp. The assembly can be provided with optional dielectric isolation parts when used in conjunction with certain functions of a wire EDM machine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns means for positioning a workpiece withinthe operating area of a machining apparatus. In particular, theinvention relates to a multi-component assembly for adjustably andrepeatably locating a workpiece at a precise location relative to amachine tool.

2. Description of the Prior Art

As the level of technology has increased, the requirement for morecomplicated, detailed and precision made parts has likewise increased.To produce such parts, a machining technology has evolved termed "wireelectrical discharge machining" or wire EDM. This technology permits themachining of complicated geometric shapes from particularly hard anddifficult to cut electrically conductive materials.

A problem with such machines, however, is that only one part at a timecan be machined. Also, the cutting speed of a wire EDM machine isrelatively slow. These disadvantages, plus the high cost of wire EDMmachines, induce a manufacturer to enhance the effectiveness of themachine as much as possible.

As a partial resolution to the above problems, operators are learning topre-rig a workpiece within a clamping assembly while the machine issimultaneously operating on another workpiece. In this way, theworkpiece changeover time is significantly reduced and the efficiency ofthe machine is greatly enhanced.

A difficulty with the above procedure is being able to quickly andprecisely locate the workpiece relative to the wire or machine tool on aconsistent and repetitive basis. This difficulty has been addressed inU.S. Pat. Nos. 4,656,326 and 4,786,776. Each of these patents describe acomplicated assembly of numerous parts which all fit together from thesurface of the machine tool table. The patents show the use of multipleplates, bridge parts, large reference blocks, miscellaneous braces andslotted clamps. Not only are the above parts cumbersome and difficult toadjust, if just one of the many parts becomes misaligned or in some waydistorted, each of the successive parts becomes exaggerated inmisalignment. Further, such systems are expensive and time-consuming touse.

SUMMARY OF THE INVENTION

The present invention provides an assembly for holding a workpiece whichcan be assembled and placed within the machine operating area with ahigh degree of accuracy. Additionally, the claimed assembly is simple touse and can engage a workpiece in a highly rigid manner which issubstantially impervious to distortion or misguided connections. It alsoprovides the ability to pre-rig a variety of workpieces outside themachine for subsequent precise placement within the machine with aminimum of time and low-skilled effort.

The invention provides a base module, which is secured to the machinetable, and a release module which is detachably connected to the basemodule. The modules comprise three basic components which adjustablyinterconnect in a cooperating relationship to each other and to aworkpiece clamping means. The first component comprises a uniquelybeveled rail which is attached to the machine work table relative topredetermined reference lines. The second component comprises a railclamp that adjustably attaches to the rail. The clamp includes a largesurface area that references against a like area on the rail to providea repeatable, stable and precisely aligned connection thereto. The clampalso includes a lever-actuated release means that allows quick and easydetachment from the third component.

The third component comprises a leveler head which includes both avertical and cant adjustment means. These adjustment means are designedto interact with the attachment region of a workpiece clamping means.The leveler head further includes reference surfaces for engagement withcorresponding surfaces on the workpiece clamping means and the railclamp. In this way, each component will be referenced to each other andto the predetermined reference lines of the machining apparatus. Withthe above three components, it follows that any workpiece secured in theworkpiece clamping means is capable of being accurately located at anydesired position relative to a machine tool or the wire of an EDMmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view showing three components of theinvention connected to a workpiece clamping means which is holding aworkpiece within the operating area of a wire electrical dischargemachining apparatus.

FIG. 2 is a top plan view of the rail of the invention shown in FIG. 1.

FIG. 3 a cross-sectional view taken along lines 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 2.

FIG. 5 is a top plan view of the rail clamp of the invention shown inFIG. 1.

FIG. 6 is a cross-sectional view taken along lines 6--6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along lines 7--7 of FIG. 5.

FIG. 8 is a cross-sectional view taken along lines 8--8 of FIG. 5.

FIG. 9 is an end elevation view taken along lines 9--9 of FIG. 5.

FIG. 10 is a cross-sectional view taken along lines 10--10 of FIG. 9.

FIG. 11 is a top plan view of the leveler head of the invention shown inFIG. 1.

FIG. 12 is a cross-sectional view taken along lines 12--12 of FIG. 11.

FIG. 13 is a left end elevational view of the leveler head shown in FIG.11.

FIG. 14 is a cross-sectional view taken along lines 14--14 of FIG. 11.

FIG. 15 is a cross-sectional view taken along lines 15--15 of FIG. 11.

FIG. 16 is a cross-sectional view taken along lines 16--16 of FIG. 11.

FIG. 17 is an isometric exploded view of the invention and the workpiececlamping means of FIG. 1 including dielectric means for electricallyisolating the workpiece clamping means from the leveler head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now FIG. 1, the overall assembly 10 of the invention isshown relative to its use on a wire EDM apparatus 26. The apparatusincludes the operative tool, shown as wire 22, which operates upon aworkpiece 20. The workpiece is held in place by a workpiece clampingmeans 18 which is secured in a predetermined fashion to the threecomponent assembly of the invention.

More particularly, the assembly comprises a leveler head 16 which isremovably attached to a rail clamp 14. The rail clamp is adjustablysecured to rail 12 which, in turn, is secured to top surface 24 of themachining apparatus.

As shown in FIG. 1, the top surface is provided with surface openings 25which are spaced-apart and aligned precisely along a predetermined xaxis. The x axis is orthogonally referenced to a y and z axis, shown byreference 8, which correspond to the exact position of machining wire22. Thus, by providing a reference surface on rail 12 which is parallelto the x or y axis and, by providing corresponding orthogonal referencesurfaces on each of the rail clamp, leveler head and workpiece clampingmeans, a workpiece can be precisely located relative to the machinetool.

With reference now to FIG. 2, the structure of rail 12 will bedescribed. Overall, it comprises a solid elongated part having a flatbottom surface 28. Extending perpendicularly from the bottom surface arefront side surface 30 and back side surface 32. The side surfaces areparallel to each other so that when the rail is aligned along theaforementioned x axis, both the front and back side surfaces willlikewise extend parallel to the x axis. Further, since the side surfacesextend perpendicular to the table surface, they will be in alignmentwith the z axis of the machine.

The rail is provided with end walls 33a,b which are parallel to eachother and extend perpendicular to bottom surface 28. Additionally, theend walls extend perpendicular to the side surfaces so that the plane oftheir surfaces will extend parallel to the y axis of the machine.

Inclining upwardly and inwardly from backside surface 32, is oblique topsurface 34. The oblique top surface extends up to a ridge line 35 whichextends longitudinally from each end wall of the rail.

The rail includes a front top surface 36 which extends from front sidesurface 30 inwardly to a merger corner 37. Inclined upwardly from themerger corner to ridge line 35 is a front face surface 38. Each of theaforementioned rail surfaces are preferably flat and extend uniformlyalong the longitudinal axis of the rail.

The rail front top surface is provided with countersunk openings 29whose center axes are spaced-apart in a longitudinal alignment which isparallel to front side surface 30. The openings are spaced-apart apredetermined distance corresponding to the previously referenced tabletop openings 25. Thus, when secured with table fasteners 31 to themachine table, as shown in FIG. 17, rail surfaces 30,32 will be alignedexactly along the machine x axis.

The rail oblique top surface 34 is provided with top openings 39.Preferably, these openings are threaded and aligned so that theircentral axes are inclined relative to bottom 28 for a purpose to behereinafter described.

With particular reference to FIGS. 5-10 of the drawings, the rail clamp14 of the invention is shown in detail. The rail clamp is generally asolid body having an inner channel 41 that overlies rail 12 whenadjustably attached thereto. The channel is defined by a front leg 42and a back leg 43. Each of the legs have a respective flat bottom legsurface 44 for resting upon the machine table. The back leg is furtherdefined by a flat inner channel surface 45 that extends perpendicularlyfrom the corresponding bottom leg surface 44 to an oblique upper surface49.

The aforementioned inner channel surface forms part of the back side ofthe inner channel cross-sectional outline which is substantiallycoextensive with, and slightly larger than, the cross-sectional outlineof rail 12. In this manner, the rail clamp will conveniently overlie therail whereby the respective outlines will have sufficient clearance topermit longitudinal movement along the axial extent of the rail forpurposes of adjustment.

The exterior outline of the rail clamp is defined by a back sidewall 57which extends upwardly from bottom leg surface 44 to an inclined topsurface 46a. The inclined top surface merges into a rail top side 46bwhich extends to outer corners 52. The outer corners define theintersection between lateral side walls 61a,b and connector faces 51.

The connector faces form part of a leveler connector means to behereinafter described. They extend perpendicularly from bottom legsurfaces 44 and are aligned parallel to inner channel surface 45. As sodisposed, it can be seen that when inner channel surface 45 is drawnagainst back side surface 32 of the rail, the connector faces will beparallel to the x and z axes of the machining apparatus 26.

To facilitate a secure and complete engagement of the rail and railclamp via backside surface 32 and inner channel surface 45, inclined topsurface 46a is provided with a countersunk elongated slot 47. The slotextends through the upper thickness of the rail clamp above, and at anacute angle relative to, the inner channel surface. The slot axis isalso coextensive with the axis of top openings 39. A threaded railfastener 48 may then be used for insertion into the slot for engagementwith corresponding threads in the openings 39.

It can be seen that because of the fastener's angular orientation, astrong force component directed perpendicular to, and inward from, innerchannel surface 45 will result as the fastener is tightened. There willalso be a downwardly directed force component to draw bottom legsurfaces 44 solidly against the machine reference table 24. Thesimultaneous action of each of the force components will produce a solidmating engagement between all of the reference surfaces.

As shown in FIG. 2, the inclined openings 39 are spaced at varyinglocations along the longitudinal extent of the rail. This allows therail clamp to be positioned above any of said openings. The rail clampmay be further adjusted longitudinally within the constraints of theelongated slot 47.

In addition to the above, the rail clamp includes a leveler connectormeans 50 for engaging the leveler head 16. The connector means comprisesopposing flat upstanding connector faces 51 which extend inwardly fromrespective outer corners 52 of the rail clamp front leg. The facesextend inwardly to a respective bevel corner 53 and incline backoutwardly to define first and second oppositely flared surfaces 54,55.Each of the flared surfaces are flat and terminate at a central frontleg face 56. The front leg face comprises a flat planar surface that isperpendicular to bottom leg surface 44 and is parallel to inner channelsurface 45. Each of the flared surfaces are also perpendicular to thebottom leg surface 44.

As best shown in FIGS. 6-8 and 10, the leveler connector means furtherincludes a locking means 58 for providing a secure and releasableconnection with the aforementioned leveler head. The locking meanscomprises an elongated pivot shaft 59 extending through a central bore60. The central bore extends transversely through about the middle ofopposing lateral side walls 61a,b of the rail clamp. The central boreaxis is preferably parallel with the connector faces and includes anenlarged area 62 which houses a cam element 63.

Extending perpendicular to the axis of the pivot shaft is lock element64. The lock element is provided with an oblong opening 65 into whichthe cam element 63 extends. As arranged, rotation of the pivot shaftwill rotate cam element 63 against the inside edges of the oblongopening. This will cause a reciprocating movement of lock element 64within the enlarged area 62.

Lock element 64 is provided with an integral outwardly flared segment 66which is coextensive with the second outwardly flared surface 55. Theflared segment is located within recess 67 of the flared surface 55. Itmay be drawn inwardly from the recess into a locking position against acorresponding surface of the leveler head upon rotation of theaforementioned pivot shaft. This action will draw rail clamp surfaces78a, 81a and 78b against the respective leveler head surfaces 51 and 54.In turn, the leveler head will become orthogonally aligned with the railclamp, rail and machine references shown by reference numeral 8.

The pivot shaft includes an outer extension 68 to which is connected alever 69. The lever conveniently allows a user to exert leverage on thepivot shaft for effecting a snug engagement of the flared segmentagainst the aforesaid corresponding leveler head surface. Preferably,the lever comprises a torque handle which is equipped with a torqueadjustment means, known in the art, that will permit a predeterminedamount of tightening without exceeding the limits of the locking meansassembly of parts.

As part of a leveler head adjustment means (to be hereinafterdescribed), front leg face 56 is provided with an outwardly extendingprojection 70. The projection includes an upwardly facing abutmentsurface 71 and is preferably located proximate the center of the lowerportion of the front leg face. The abutment surface is also preferablyflat and parallel with bottom leg surfaces 44.

The leveler head 16 of the invention will now be described withparticular reference to FIGS. 11-16. It comprises a generally solid bodyhaving an overall quadrilateral outline encompassing a connector portion75 and an attachment portion 76.

The connector portion has a flat base area 74 from which extend opposingflat upstanding leveler faces 78a,b. The faces are perpendicular to thebase area and extend inwardly from connector corners 79a,b tocorresponding inner edges 80a,b. Respective outwardly angled surfaces81a,b incline from the inner edges back outwardly a predetermineddistance to a flat inner-face 82. As above-described, the angledsurfaces, inner-face and leveler faces have a cross-sectional outlineabout identical to the corresponding outline of the leveler connectormeans 50. In this way, when the leveler head and rail clamp are engaged,the corresponding surfaces of each component can abut against eachother.

The leveler head connector portion is provided with a verticaladjustment means 86 which engages the previously described abutmentsurface 71 of rail clamp projection 70. The adjustment means includes arecessed portion 83 which extends upwardly from base area 74 into thecenter part of inner face 82. It has a depth sufficient to accommodatethe aforesaid projection 70 during engagement of the rail clamp andleveler head.

A vertical threaded screw opening 87 is provided extending from the topof the connector portion behind inner face 82 into the above-describedrecessed portion. Extending through the screw opening is a verticaladjustment screw 88 which has a free end 89. Rotation of the screw willcause the free end to operate against the abutment surface 71 and causethe overall leveler head to move vertically along its connection withthe rail clamp. The screw opening 87 is preferably countersunk toaccommodate the head of the screw and a compression spring 90. Thisprevents unwanted turning of the screw once the vertical heightadjustment has been made.

Attachment portion 76 of the leveler head includes a downwardly-facingattachment surface 77. This surface is flat and perpendicular to levelerfaces 78a,b. It is parallel to base area 74 and is vertically offsetabove the base area by an inside wall 85. The wall is flat andperpendicular to the attachment surface and is parallel to leveler faces78a,b. From the inside wall, the attachment surface extends outwardly todefine an underlying attachment area 84 for engaging a workpiececlamping means.

For explanatory purposes, a vise 18 and solid block 20 have been shownin FIGS. 1 and 17 as being illustrative of a workpiece and workpiececlamping means. It will be appreciated, however, that the specificclamping means being used will be dictated by the physical character ofthe workpiece and the type of machining being done. It is only importantthat the clamping means include a leveler head attachment region 19 asdescribed hereinafter.

With reference to FIG. 17, vise 18 is shown which, in its most basicform, comprises a solid body 113 with an integral stationary jaw 115. Amovable jaw 114, operated by a screw (not shown) is used to holdworkpiece 20 in a predetermined manner. The vise rear wall 21 ispreferably flat and perpendicular to the flat top surface of attachmentregion 19. It may also be parallel to a front wall surface 28 againstwhich a workpiece can be abutted.

For adjustably securing a workpiece clamping means to the aforesaidattachment area, the leveler head is provided with a cant adjustmentmeans, a lateral adjustment means and a securement means. The cantadjustment means functions to angularly orient a workpiece clamp, andworkpiece clamped thereto, relative to a machine tool. Basic elements ofthe cant adjustment means comprises a pivot contact and two verticallyadjustable contacts each of which are spaced from each other in atriangular pattern about the leveler head attachment portion 76. Thecontacts engage attachment region 19 of the workpiece and function toeffect a tilting of the workpiece clamping means as needed for properalignment.

With particular reference to FIGS. 11-17, the pivot contact is shown bya ball 92 which is constrained within seat 93. The ball and seat arepositioned adjacent leveler corner 94 and extend from surface 77 intothe underlying attachment area 84.

To provide a first one of said adjustable contacts, a first jack screwopening 96a is located at leveler corner 95. This corner is directlyopposite corner 94 along a line coextensive with leveler head outer end104. Threadably engaged in the opening is first jack screw 96b having adistal end 97.

Proximate the midpart of the leveler head attachment portion is thesecond adjustable contact comprising second jack screw opening 98a.Threadably engaged in the opening is a second jack screw 98b having adistal end 99. The location of this jack screw is offset from animaginary line extending through the ball and first jack screw so thatthe triangular pattern between the three parts is completed.

The previously mentioned lateral adjustment means provides horizontaladjustment of the workpiece clamping means relative to the leveler head.It comprises a cam shaft 105 which rotates within a bushing 110 about anaxis that is perpendicular to the attachment surface 77. The bushing islocated within aperture 106 which extends through the attachment portionof the leveler head.

The cam shaft includes an oblong-shaped cam part 107 at its free endportion which extends below the attachment surface. It engages acorresponding oblong cam socket 108 in the surface of the attachmentregion 19 of the workpiece clamping means.

The upper end of the cam shaft is provided with means for rotating theshaft about its longitudinal axis. As shown, this comprises a hex socket109 for allowing insertion of a manually operated implement.

With reference to FIGS. 11 and 15-17, the above-mentioned securementmeans will be described. This means comprises threaded fastener parts100a,b that pass through corresponding openings 101a,b in the attachmentregion. The fastener parts engage corresponding threaded openings 102a,bin the leveler head. The fastening parts operate in conjunction with thecant and lateral adjustment means whereby once both of the adjustmentmeans have the workpiece 20 in the desired position, the fastening partscan be tightened to lock together the leveler head and workpiececlamping means.

To facilitate the adjustment process, the fastener parts are preferablyprovided with biasing elements shown as spring washers 103a,b. Thespring washers allow minor adjustments while at the same time inhibitingunwanted loosening of the assembly.

When the assembly of the invention is being used in conjunction with awire EDM apparatus, it is sometimes necessary to electrically isolatethe workpiece from the assembly and its connection to the machine table.The invention is readily adaptable to this circumstance whereby theleveler head and workpiece clamping means are provided with dielectricmeans to simply and effectively achieve the desired isolation.

As shown in FIG. 17, the dielectric means comprises a dielectric gasket120 which is interposed between the attachment region 19 and attachmentsurface 77. It also includes dielectric sleeves 121a,b extending intoopenings 101a,b. Additionally, camshaft bushing 110 is constructed of adielectric material. Still further, inside wall 85 is provided withdielectric posts 112 and pivot ball 92 is constructed of a dielectricmaterial. Finally, attachment region 19 is provided with dielectric pads124a,b for electrically isolating distal ends 97, 99 of the jackscrews.

To achieve the same precise referencing as with inside wall 85, thedielectric posts 112 will have outer ends which are precision machinedto be flat and parallel to leveler faces 78a,b. In all other respects,the leveler head workpiece clamping means will interconnect and adjustin a normal fashion.

For purposes of describing operation of the assembly and, assuming thevise shown is the desired clamping means, workpiece 20 will be insertedtherein and secured in the desired position with moveable jaw 114. Theleveler head will then be placed over attachment region 19 and fastenerparts 100a,b will be passed through openings 101a,b and form a threadedengagement with threaded openings 102a,b. The fasteners will bring thetop surface of attachment region 19 into slight engagement with pivotball 92 and leveler head attachment surface 77 or with first and seconddistal ends 97, 99 and pivot ball 92. In this position, connectorportion 75 of the leveler head is slipped down over the levelerconnector means 50 of the rail clamp. Lever 69 is moved to a closedposition whereby flared segment 66 will move inwardly away from recess67 and push leveler faces 78a,b tightly against connector faces 51. Itwill also move angled surface 81a against flared surface 54.

Assuming the rail clamp has already been pre-located and securelyfastened to the rail as described previously, the workpiece may now bemore precisely positioned relative to the machining tool. This step isaccomplished by utilizing the previously described multiple adjustmentcapabilities of the leveler head. Upon achieving the desired location,the fastener parts 100a,b are then finally tightened.

From the above, it can be seen that the leveler head, vise and workpieceform a convenient partial assembly that can be pre-rigged at an assemblystation outside the machining apparatus. This can be accomplished with asimulated rail clamp stand (not shown) which has been positioned on aflat work table along the same orthogonal reference lines as those usedby the machining apparatus. Thus, as soon as the machine is finishedwith one workpiece, it can be quickly removed and replaced with another.And, regardless of the specific items being worked upon, or the specificmachining tool being utilized, the invention provides for the rapidexchange of workpieces at predetermined precisely located positions.

While the invention has been described with respect to preferredembodiments, it will be apparent to those skilled in the art thatvarious modifications and improvements may be made without departingfrom the scope and spirit of the invention. Accordingly, it is to beunderstood that the invention is not to be limited by the aforementionedspecific illustrative embodiments, but only by the scope of the appendedclaims.

I claim:
 1. A machine workpiece holding assembly having a machine tablecomprising:a base module comprising a rail secured to said machine tableand a rail clamp secured to said rail, said rail clamp having a levelerconnector means for releasably engaging a leveler head; and, a releasemodule detachably connected to said base module comprising a levelerhead having an attachment portion and a connector portion releasablyengaged with said leveler connector means and, a workpiece clampingmeans for holding a workpiece having an attachment region connected tosaid leveler head attachment portion, said leveler head including a cantadjustment means for angularly orienting said workpiece clamping meanscomprising a pivot contact and two vertically adjustable contacts whichare spaced from each other in a triangular pattern about said attachmentportion.
 2. The assembly of claim 1 wherein said rail clamp hasupstanding connector faces and said leveler head has upstanding levelerfaces and said leveler connector means includes a locking means fordrawing said leveler faces against said connector faces.
 3. The assemblyof claim 1 wherein said attachment region includes a cam socket and saidleveler head includes a lateral adjustment means for moving saidworkpiece clamping means horizontally relative to said leveler headcomprising a cam shaft rotatably mounted in said leveler head attachmentportion having a cam part extending below said attachment portion intosaid cam socket.
 4. A workpiece holding assembly for positioning aworkpiece at a predetermined position within the operating area of amachining apparatus comprising:a rail attached to said apparatus havinga reference side surface in alignment with a reference line of saidapparatus; a rail clamp having a leveler connector means with connectorfaces engaging a leveler head, said rail clamp including an innerchannel with an inside wall abutting said side surface, said connectorfaces and inside wall being orthogonally referenced to each other; aleveler head releasably secured to said connector means having aconnector portion with leveler faces abutted against said connectorfaces, said leveler head including an attachment surface orthogonallyreferenced to said leveler faces and a cant adjustment means toangularly orient said head relative to the rail clamp.
 5. The assemblyof claim 4 wherein said cant adjustment means comprises a pivot contactand two vertically adjustable contacts arranged in a triangular patternabout said attachment surface.
 6. The assembly of claim 4 wherein saidleveler head includes a lateral adjustment means for moving saidworkpiece clamping means horizontally relative to said leveler head. 7.A workpiece holding assembly for a metal machining apparatus having amachine tool and a work table with a table surface orthogonallyreferenced to said tool comprising:a rail secured to said work table,said rail being defined by a flat bottom surface from whichperpendicularly extend front and back side surfaces, said side surfacesbeing parallel to each other and extending between opposing end walls,an oblique top surface inclined upwardly from said back side surface toa ridge, a front top surface extending from said front side surface to amerger corner, a front face surface extending from said merger corner tosaid ridge, said flat bottom surface lying flat upon said table surfaceso that said side surfaces are perpendicular to said table surface andare positioned in a predetermined orientation relative to said tool; arail clamp adjustably attached to said rail, said rail clamp having aninner channel overlying said rail defined by front and back legs eachwith a flat bottom leg surface for resting upon said table, said backleg having a flat inner channel surface that extends perpendicularlyfrom a respective bottom leg surface and forms part of a cross-sectionaloutline of said inner channel that is substantially coextensive with thecross-sectional outline of said rail; said rail clamp including aleveler connector means comprising opposing flat upstanding connectorfaces that extend inwardly from respective outer corners of the frontleg in a manner that is perpendicular to corresponding bottom legsurfaces and parallel with said inner channel surface to respectivefirst and second oppositely flared surfaces which are joined by a frontleg face, each of said first and second flared surfaces and said frontleg face are perpendicular to the bottom leg surfaces; and, a levelerhead adjustably connected to said leveler connector means having a basearea and a connector portion extending above the base area and anattachment portion that includes a downwardly facing attachment surfacethat is parallel to the bottom leg surfaces of said rail clamp and isoffset above and outward from said base area, said connector portioncorresponding in cross-sectional shape to the cross-sectional shape ofsaid leveler connector means including respective opposing flatupstanding leveler faces that abut against corresponding connector facesof the leveler connector means, said leveler faces terminating atrespective inner edges from which extend respective outwardly angledsurfaces which engage the corresponding first and second flared surfacesof said leveler connector means, said angled surfaces terminating at aleveler head inner face which abuts against the front leg face of saidleveler connector means, the front leg face of said leveler connectormeans including an outwardly extending projection having an abutmentsurface, said leveler head connector portion including verticaladjustment means that engages said abutment surface for verticallymoving said leveler head.
 8. The assembly of claim 7 wherein said basearea includes an recessed portion into which said projection extends,said vertical adjustment means comprising an adjustment screw extendingthrough a vertical threaded screw opening in said connector portionhaving a screw end that engages said abutment surface.
 9. A workpieceholding assembly for a metal machining apparatus having a machine tooland a work table with a table surface orthogonally referenced to saidtool comprising:a rail secured to said work table, said rail beingdefined by a flat bottom surface from which perpendicularly extend frontand back side surfaces, said side surfaces being parallel to each otherand extending between opposing end walls, an oblique top surfaceinclined upwardly from said back side surface to a ridge, a front topsurface extending from said front side surface to a merger corner, afront face surface extending from said merger corner to said ridge, saidflat bottom surface lying flat upon said table surface so that said sidesurfaces are perpendicular to said table surface and are positioned in apredetermined orientation relative to said tool; a rail clamp adjustablyattached to said rail, said rail clamp having an inner channel overlyingsaid rail defined by front and back legs each with a flat bottom legsurface for resting upon said table, said back leg having a flat innerchannel surface that extends perpendicularly from a respective bottomleg surface and forms part of a cross-sectional outline of said innerchannel that is substantially coextensive with the cross-sectionaloutline of said rail; said rail clamp including a leveler connectormeans comprising opposing flat upstanding connector faces that extendinwardly from respective outer corners of the front leg in a manner thatis perpendicular to corresponding bottom leg surfaces and parallel withsaid inner channel surface to respective first and second oppositelyflared surfaces which are joined by a front leg face, each of said firstand second flared surfaces and said front leg face are perpendicular tothe bottom leg surfaces: and, a leveler head adjustably connected tosaid leveler connector means having a base area and a connector portionextending above the base area and an attachment portion that includes adownwardly facing attachment surface that is parallel to the bottom legsurfaces of said rail clamp and is offset above and outward from saidbase area, said connector portion corresponding in cross-sectional shapeto the cross-sectional shape of said leveler connector means includingrespective opposing flat upstanding leveler faces that abut againstcorresponding connector faces of the leveler connector means, saidleveler faces terminating at respective inner edges from which extendrespective outwardly angled surfaces which engage the correspondingfirst and second flared surfaces of said leveler connector means, saidangled surfaces terminating at a leveler head inner face which abutsagainst the front leg face of said leveler connector means wherein theattachment portion of said leveler head includes fastening means foradjustably securing a workpiece clamping means to said leveler head andsaid fastening means includes a cant adjustment means for orienting saidworkpiece clamping means relative to said machining tool.
 10. Theassembly of claim 9 wherein said attachment surface is vertically offsetfrom said base area by an inside wall to provide an underlyingattachment area, said workpiece clamping means being secured to saidleveler head at said attachment area.
 11. The assembly of claim 9wherein said cant adjustment means comprises a pivot contact and twovertically adjustable contacts with each contact being spaced from eachother in a triangular pattern about the leveler head attachment portion.12. The assembly of claim 11 wherein said pivot contact extendsdownwardly from an outer corner portion of said clamp attachment surfaceand at least one of said vertically adjustable contacts extendsdownwardly from an opposing outer corner portion of said attachmentsurface.
 13. The assembly of claim 11 wherein said fastening meansincludes at least one fastening part stationarily securing the workpiececlamping means to said leveler head at a location within the areadefined by said triangular pattern.
 14. The assembly of claim 12 whereineach of said vertically adjustable contacts comprises a jackscrew with adistal end and said pivot contact comprises a pivot ball.
 15. Theassembly of claim 9 including a lateral adjustment means interconnectingsaid leveler head with the workpiece clamping means for adjustablymoving said workpiece clamping means about a horizontal plane parallelwith the attachment surface.
 16. The assembly of claim 15 wherein saidlateral adjustment means comprises a cam shaft rotatable within anaperture through said attachment portion about an axis that isperpendicular to said attachment surface, said cam shaft having a campart at a free end portion extending below said attachment surface, saidcam part being adapted to extend into a cam socket at a predeterminedlocation on the workpiece clamping means.
 17. A workpiece holdingassembly for positioning a workpiece at a predetermined position withinthe operating area of a machining apparatus comprising:a rail attachedto said apparatus having a reference side surface in alignment with areference line of said apparatus; a rail clamp having a levelerconnector means with connector faces engaging a leveler head, said railclamp including an inner channel with an inside wall abutting said sidesurface, said connector faces and inside wall being orthogonallyreferenced to each other; a leveler head releasably secured to saidconnector means having a connector portion with leveler faces abuttedagainst said connector faces, said leveler head including an attachmentsurface orthogonally referenced to said leveler faces, said levelerconnector means including a front leg face with an outwardly extendingprojection, said leveler head having a vertical adjustment means thatoperates in conjunction with said projection to vertically move saidleveler head relative to said rail clamp; and, a workpiece clampingmeans having an attachment region in engagement with said attachmentsurface, said workpiece clamping means holding the workpiece in apredetermined position within said operating area.
 18. A workpieceholding assembly for positioning a workpiece at a predetermined positionwithin the operating area of a machining apparatus comprising:a railattached to said apparatus having a reference side surface in alignmentwith a reference line of said apparatus; a rail clamp having a levelerconnector means with connector faces engaging a leveler head, said railclamp including an inner channel with an inside wall being orthogonallyreferenced to each other; a leveler head releasably secured to saidconnector means having a connector portion with leveler faces abuttedagainst said connector faces, said leveler head including an attachmentsurface orthogonally referenced to said leveler faces, said levelerconnector means including a locking means for releasably securing saidleveler head to said rail clamp comprising a handle actuated lockelement which is movable against a corresponding surface of the levelerhead; and, a workpiece clamping means having an attachment region inengagement with said attachment surface, said workpiece clamping meansholding the workpiece in a predetermined position within said operatingarea.
 19. A machine workpiece holding assembly having a machine tablecomprising:a base module comprising a rail secured to said machine tableand a rail clamp secured to said rail, said rail clamp having a levelerconnector means for releasably engaging a leveler head; and, a releasemodule detachably connected to said base module comprising a levelerhead having an attachment portion and a connector portion releasablyengaged with said leveler connector means, said leveler connector meansincluding a front leg face with an outwardly extending projection, saidleveler head having a vertical adjustment means that operates inconjunction with said projection to vertically move said leveler headrelative to said rail clamp and, a workpiece clamping means for holdinga workpiece having an attachment region connected to said leveler headattachment portion.